As a result of both the increasing demand from consumers for additional ‘smart’ functionality in spray products, and the ever-growing pressure to eliminate the greenhouse gas propellants inherent to traditional aerosol can technology, alternatives to traditional spray technologies are being sought. This has led to rapid growth in the field of electronic spray technologies such as that disclosed in PCT/GB92/02262. These devices bring environmental benefits as they do not require propellants and, because the spray is electronically generated, they provide repeatable, controllable performance.
For many applications such electronic spray products can be required to deliver high flow rates, operate in multiple or all orientations, and operate with the spray head above the bulk of the fluid in the primary operating orientation. Further, such fluid feeds should ensure that almost all of the fluid initially contained within the product's fluid reservoir can be sprayed, i.e. minimise residual fluid when the product stops functioning at an acceptable level. The move towards more compact products drives the fluid feed system to be space-efficient and, finally, a requirement on the user to prime the spray product manually should be avoided as this reduces the product's consumer appeal and the repeatability of the spray.
Thus there is a requirement for fluid feed designs which can deliver high flow rates in many or all orientations to such electronic spray heads that do not require a priming operation and that minimise un-sprayable residual fluid.
Many examples of fluid feed systems for spray devices are known in the art. For example, dip tubes are commonly used in manually pumped spray heads, for example U.S. Pat. No. 5,518,150 and U.S. Pat. No. 6,202,943. Dip tubes are also used in highly pressurised reservoirs for aerosol type applications as disclosed in U.S. Pat. No. 4,966,313. However such systems are not in general suitable for feeding electronic spray heads. Electronic spray heads generally will not pump air: if air gets into the dip tube then the device may fail.
To counter this problem porous media, generally in the form of wicks, have been used to deliver air-freshener formulations to electronic spray heads for example EP1159078 and PCT/GB92/02262. An advantage of these systems is that they can be self-priming, but a related drawback of these systems is that they can deliver only relatively low flow-rates and are generally restricted in the range of orientations in which they operate effectively.
A mechanically operated suction pump has been used to draw fluid against gravity to deliver it to an electronic spray head, as described in WO9729851. This approach enables the fluid to be drawn up to the electronic spray head in bulk, thereby enabling the desired high flow-rates to be achieved; however a drawback related to these systems is that they require a manual priming operation.
The prior art has attempted to overcome some of the drawbacks of these systems by the use of sponge-filled reservoirs for fluid delivery to an electronic spray head in WO06066671 and PCT/GB92/02262. Such systems can help to increase the range of orientations in which the spray can operate, but suffer from a degradation of spray delivery with time as the amount of fluid in the reservoir reduces, and these systems tend to result in a high level of residual fluid remaining in the sponge which cannot be dispensed.